The proposed research investigates the effects of early unilateral brain lesions on subsequent neuro-cognitive development. Numerous studies have shown that age at the time of the brain damage has significant effects on the functional consequences of the damage. However, for the most part each study has investigated the effects of lesions on cognitive functioning at only a single point in time, providing only a "snapshot" of the consequences of the brain damage. This is particularly problematic when the brain damage is superimposed on a developed brain. The proposed research examines the effects of elapsed time since the brain damage on cognitive functioning in hemiplegic children with congenital lesions. Preliminary cross-sectional data suggest that elapsed time since lesion is an important factor in predicting the cognitive functioning of these children. In particularly, the overall IQ of these children appears to differ significantly from normals after, but not before age 7 - 8. Longitudinal information on the neuro-cognitive consequences of congenital unilateral lesions will be obtained by administering a broad range of cognitive and neurological tests to two groups of children we have already tested: 1) children with congenital unilateral brain lesions confirmed by CT-scans 2) children who do not have structural lesions, but who are matched to the brain damaged children for age, sex, race, socio-economic status and IQ at initial testing. Inclusion of such a control group will allow us to determine whether any changes in pattern or level of intellectual functioning over time are specific to early unilateral brain damage or rather, are IQ-level specific. In addition to cognitive and neurological tests, hemiplegic children will receive EEGs. This will allow us to relate EEG and/or seizure abnormalities to neuro-cognitive development. Finally, hemiplegic children will receive MRI studies in order to relate our understanding of the neuro- cognitive consequences of early brain lesions for the developing child should provide information about the time course of functional maturation of the nervous system as well as leading to better long-term planning of remediation programs for brain damaged children.